1. Field of the Invention
The present invention relates to agricultural implements, and more particularly to a new seed plate for precisely picking up seeds from a hopper and depositing them one at a time into a furrow formed in the ground.
2. Description of the Prior Art
In the past, certain types of seeds, for instance vegetable seeds, were placed rather closely together within furrows formed in the ground. To achieve maximum yield, after the seeds sprouted, the plants were thinned so that only a single plant was allowed to grow at any location and so that the spacing between plants was uniform. If two or more plants were allowed to grow at a particular location, they would not mature properly thereby resulting in a significantly smaller, poor quality vegetable.
In recent years, to eliminate the expense and time required to manually thin the plants, precision seeders have been developed to theoretically deposit only one seed at a time into the ground. One known type of such seeding mechanism includes a vertical hopper mounted on a wheeled frame which is pulled behind a tractor. A vertically oriented, circular, rotating seed plate or wheel, having a plurality of seed receiving cells formed about its circumference, is disposed either partially within the seed hopper or at least in communication with the seed hopper. The portion of the seed plate disposed externally of the hopper is rotatably journaled within a closely fitting housing having a seed outlet opening in its bottom. As the seed plate rotates through the hopper, a single seed is theoretically picked up by each cell and then carried upwardly around the circumference of the plate and then downwardly until it drops through the outlet opening at the bottom of the seed plate housing. The closely fitting housing prevents seeds from falling off the seed plate before reaching the housing outlet opening.
Seed cells of various configurations have been formed in vertical seed plates. One known type of seed cell is shaped similar to ratchet teeth, each cell having a radially disposed trailing face and a leading angular face extending from the inner end of the radial face forwardly in the direction of rotation of the plate. A spherical recess or pocket is formed in the trailing radial face for receiving a single seed therein. Ideally the seed remains in the cell pocket until the cell is in its downward travel. Examples of seed plates utilizing this type of cell are disclosed by Wechsler, U.S. Pat. No. 2,645,385; and Raught, U.S. Pat. No. 2,667,286.
In another type of vertical seed plate formed with ratchet teeth shaped cells, a seed pocket for receiving a seed therein is formed in the root portion of each cell, at the intersection of the radial and angular cell faces. An example of a seed plate utilizing this type of cell configuration is disclosed by U.S. Pat. No. 2,980,043 to Beck.
One drawback of seed plates utilizing ratchet teeth shaped seed cells with a seed receiving pocket formed therein is that if the pocket is formed in a size corresponding to the average size of the particular type of seed being planted, larger seeds will not fit within the pocket so they either are crushed or they fall out of the pocket causing a skip or miss to occur in the row of plants. Alternatively, if the cell is formed in a size substantially larger than the nominal size of the seeds to thereby increase the possibility that a seed will be picked up by each cell, more than one smaller sized seed at a time might lodge within the pocket so that a double or even triple set of plants could sprout at one location. When this occurs, the plants must be manually thinned. Furthermore, since the seed pocket normally does not occupy the entire surface area of each cell face, additional seeds may lodge on the portions of the seed cell surfaces surrounding the pocket resulting in several seeds simultaneously dropping onto the ground.
In a further type of vertically disposed seed plate, hook-shaped cells are spaced around the circumference of the plate. Each of these hook-shaped cells includes a short, radially extending trailing surface, an arcuate surface disposed radially inwardly from the trailing surface, a radially disposed leading surface and an intermediate surface interconnecting the arcuate surface with the leading surface. A generally semi-circular shaped seed-receiving pocket is formed in the trailing surface of each seed cell. The seed pocket opens circumferentially forwardly in the direction of rotation of the seed plate. The faces of the seed plate are beveled in the region of the arcuate surface of each seed cell, in a manner similar to the blade of a knife, to form a central edge of insufficient width to support a seed therealong. In operation, as a seed cell travels upwardly through a hopper, a seed is theoretically lodged within the pocket formed in the cell trailing surface. However, the beveled arcuate portion of the seed cell prevents additional seeds from being lodged thereon. As the cell reaches the top of the travel of the plate, the seed falls out of the pocket and down onto the intermediate cell surface. Then, as the cell begins to travel downwardly, the seed rolls down to the transversely flat, leading surface of the cell, at which location the seed is supported until it drops out of an opening provided at the bottom of the seed plate housing. Although this particular seed cell design might reduce the possibility that more than one seed at a time may be picked up by a cell, it is also quite possible that as the cell rotates through the hopper no seed may actually lodge within the cell pocket. If this occurs, a skip will exist in the row of plants. An example of a seed plate utilizing this particular type of cell configuration is disclosed by Grimsbo, U.S. Pat. No. 2,855,125.
In another type of vertically disposed seed plate, semi-circularly shaped cells are formed in the circumferential rim portion of the plate. Each of the cells is open in the direction facing radially outwardly from the plate to receive a seed therein as the plate rotates through the hopper. The seed deposited with the cell travels along the circular path swept by the cell and then falls downwardly out an opening provided at the bottom of the seed plate housing. Because the seed cell must be formed large enough to accommodate the larger sized seeds within the hopper, not uncommonly two or even three more smaller seeds at a time occupy a single cell. Furthermore, even though the pockets might be formed in a size generally approximately the size of the largest seeds in the hopper, it is possible that two or three large seeds could be clustered together adjacent the rim of the seed plate so that none of the seeds actually drop into a passing cell. An example of this type of seed plate is disclosed by U.S. Pat. No. 2,679,950 to Swanson.
The above mentioned seed plates all rotate within a closely fitting housing. Consequently, as a seed cell rotates by the hopper, seeds are often clustered at the location where the plate enters the housing. Then, due to debris or oversized seeds in the area, the clustered seeds cannot move away from the housing but become trapped and crushed between the plate and the housing sidewall or cut by an edge of a passing cell end wall.
In another type of seeder, a cylindrically shaped hopper is mounted on a wheeled frame structure which in turn is pulled by a tractor. Rather than being mounted vertically, the hopper is tilted rearwardly so that the seeds collect in the lowermost portion of the inclined hopper. A circularly shaped seed plate is located just above the bottom of the hopper. The seed plate closely fits within the inside diameter of the hopper and is orientated at the same slope as the bottom of the hopper. Seed receiving cells in the shape of saw teeth are formed around the circumference or periphery of the inclined seed plate. The seed plate is powered to rotate through the seeds located within the hopper to ideally capture a single seed within the cavity formed by the seed cell and the inside diameter of the hopper, and then carry the seed up the inclined hopper bottom and deposit it within an outlet opening formed at the top of the incline. From the outlet opening, the seed travels through a delivery tube and into a furrow dug by a cultivator shoe traveling in front of the hopper.
Under ideal conditions, one seed at a time is captured within each seed cell. Unfortunately, however, seeds of a particular crop are not always of uniform size and shape. Thus, the seed plate cell must be sized large enough to accommodate the largest seeds. Even so, not infrequently a seed is not captured by a seed cell as the plate rotates through the lowest level of the hopper causing a skip in the row of plants. Moreover, it is not uncommon for more than one smaller sized seed at a time to be captured by a cell and deposited in the hopper outlet opening. This results in the growth of multiple plants which must be thinned by hand. An example of a seeder utilizing this particular type of seed plate is the Model 33 Vegetable Planter manufactured by John Deere and Company.
Accordingly, it is a primary object of the present invention to provide an improved seed plate which is especially adapted to precisely deposit one seed at a time into the ground.